Digital and analog data communications over conventional utility and premises electric power lines is an established method for point-to-point and point-to-multipoint communications between devices. In such communications, a communication signal carrying data is superimposed on a 50 to 60 Hz alternating current (AC) power line using higher frequencies. A central computer may use such a power line communications system to control remote power applications, to monitor remote utility usage, or to support energy conservation. For example, the central computer may control the operation of heaters, air-conditioners, electric lighting and the like. The power line communications system may also be used to support high-speed broadband data to support Internet, multimedia and home entertainment systems, using a power line communication network such as IEEE 1901, IEEE P1901.2, HomePlug GP/AV/AV2/1.0, G.hn, G.hnem, and other similar technologies.
The throughput of a power line communication link, such as a link between two modems or network nodes, may be affected by environmental electrical interference and may suffer degradation when the level of interference is high. For example, when an appliance, such as a television or computer, is attached to the power line in the general proximity of the point where the modem is attached to the same power line, switching noise from the switched-mode power supply of the appliance may create disturbances on the power line that reduce the signal to noise ratio and the bandwidth available to the power line modem. In some cases, these disturbances may be exacerbated when there is high attenuation of data signals superimposed on the power line.